1. Field of the Invention
The present invention relates to the field of liquid crystal displaying, and in particular to a heat sink and a backlight module using the heat sink.
2. The Related Arts
Liquid crystal display (LCD) has a variety of advantages, such as thin device body, low power consumption, and being free of radiation, and is thus widely used. Most of the LCDs that are currently available in the market are backlighting LCDs, which comprise a liquid crystal panel and a backlight module. The operation principle of the liquid crystal panel is that liquid crystal molecules are interposed between two parallel glass substrates and the liquid crystal molecules are controlled to change direction by application of electricity to the glass substrates in order to refract out light emitting from the backlight module for generating images. Since the liquid crystal panel itself does not emit light, light must be provided by the backlight module in order to normally display images. Thus, the backlight module is one of the key components of an LCD. The backlight module can be classified in two types, namely side-edge backlight module and direct backlight module, according to the position where light gets incident. The direct backlight module comprises a light source, such as a cold cathode fluorescent lamp (CCFL) or a light-emitting diode (LED), which is arranged at the back side of the liquid crystal panel to form a planar light source that directly provides lighting to the liquid crystal panel. The side-edge backlight module comprises a backlight source, such as an LED light bar, arranged at an edge of a backplane to be located rearward of one side of the liquid crystal panel. The LED light bar emits light that enters an optic film assembly through a light incident face of the optic film assembly and is projected out of a light emergence face of the optic film assembly, after being reflected and diffused, to thereby form a planar light source for the liquid crystal panel.
In the heat dissipation design of the conventional side-edge LED backlight module, an LED light bar mounted to a heat sink by being fixed by bolts or bonded by thermal grease. The heat sink is then mounted to a backplane. Heat is transmitted from the light bar to the heat sink for dissipation. As shown in FIG. 1, which is a schematic view showing the structure of a conventional heat sink for LED light bar, the heat sink 100 comprises a bottom plate 102 and a side plate 104. The bottom plate 102 and the side plate 104 are generally integrally formed of aluminum extruded material. An LED light bar 300 is mounted to the side plate 104. Heat emitting from the LED light bar 300 is transmitted through the side plate 104 to the bottom plate 102 and is dissipation through a large area of the bottom plate 102. To provide bettered heat dissipation performance, the bottom surface 102 is made of a large surface area. Generally, the width a of the bottom plate 102 is increased to expand the surface area of the bottom plate 102. However, the technical limitation of the aluminum extrusion art makes the aluminum extrusion poor in flatness if the extruded thickness is excessively small. When the width a is increased, the thickness of the bottom plate 102 must be increased correspondingly, otherwise it is difficult for the process to make an extrusion with excellent flatness. However, increasing the thickness of the bottom plate 102 will consume more aluminum extrusion material. Further, increasing the width a will require an aluminum extrusion machine of greater tonnage, and thus the cost is increased. Particularly, the increase of cost is even more significant for the heat dissipation solution for high power light bars.